1. Field of the Invention
The present invention relates to a fuel composition containing (a) a medium substantially free of to free of sulphur; (b) a detergent/dispersant additive; and (c) a liquid fuel. The invention further provides a process for increasing the efficiency of an exhaust after-treatment device of an internal combustion engine and a process for preparing a fuel composition comprising the medium substantially free of to free of sulphur.
2. Description of the Related Art
Global legislation towards a reduction of certain components of exhaust emissions, including NOx (nitrogen oxides) and particulate matter such as soot and oxides of sulphur, produced by automotive engines has resulted in a decrease in the sulphur content of fuel such as diesel fuel and gasoline since the sulphur upon combustion produces highly acidic products and can interfere with the functioning of exhaust after-treatment devices of internal combustion engines. In many countries the sulphur content of fuel has been or is being decreased to less than about 50 ppm and newer fuels have even lower sulphur contents of about 20 ppm or less. Fuels with a sulphur content of about 20 ppm or less are often referred to as ultra-low sulphur fuels.
Furthermore in an attempt to meet emissions targets, automotive manufacturers are developing exhaust after-treatment devices to further reduce emissions. These exhaust after-treatment devices are known to be susceptible to sulphur poisoning even at low sulphur concentrations from sulphur-containing components evolved during fuel combustion. As a consequence of sulphur poisoning, exhaust after-treatment devices may be less efficient which can decrease the performance of the engine and can increase the amounts of regulated components, such as NOx and particulate matter and hydrocarbons and carbon monoxide, emitted from the exhaust of the engine.
The patent literature is replete with disclosures of fuel compositions comprising mediums and detergent/dispersant additives.
Duncan et al. in International Publication No. WO 02/06428A1 disclose an additive composition for improving middle distillate fuel oils that comprises a hydrocarbyl-substituted monosuccinimide dispersant and an oil having a viscosity at 40° C. of about 100 to about 400 centistokes.
Wallace in European Publication No. EP 0476196A1 discloses a fuel composition having improved combustion characteristics that comprises a liquid hydro-carbonaceous fuel, a manganese carbonyl compound, an alkali or alkaline earth metal containing detergent, an ashless dispersant and optionally other components.
International Publication WO 98/12282 A1 discloses a detergent additive composition for diesel fuel that contains a polyisobutylene monosuccinimide in an aromatic hydrocarbon diluent. The detergent additive composition can be used to remove or prevent engine deposits.
U.S. Pat. No. 5,279,626 discloses an additive package with an enhanced shelf-life stability that contains (a) a dispersant/detergent; (b) a demulsifier; and (c) a solvent stabilizer formed from at least one aromatic hydrocarbon solvent and at least one alcohol.
U.S. Pat. No. 3,658,494 discloses a fuel composition and a solution in a solvent where the fuel composition or solution contains an additive combination comprising an oxy compound and a dispersant. The fuel composition can be prepared from the solution of the oxy compound and dispersant in the solvent. The fuel composition or solution can be used to clean fuel systems in liquid-fuel burning devices such as internal combustion engines.
Chamberlin, III et al. in U.S. Pat. No. 6,408,812 disclose the combining of a used lubricating oil composition with a gasoline fuel composition for consumption by a spark-ignited internal combustion engine having an exhaust gas after-treatment device where the oil composition is free of sulphur, phosphorus, halogens and metals.
When the medium is an aromatic solvent or diluent, such as for example a xylene or toluene which have low flash points, compositions and processes using such a medium can suffer from lower processing temperatures and/or increased flammability risks. In principle higher molecular weight aromatic compounds with higher flash points may be used. However, many of these aromatic compounds have toxicity issues such as being carcinogenic.
It would be desirable to have a composition and process employing a medium that increases the flashpoint of the composition and the safety of the process. The present invention provides such a composition and process.
It would be desirable to have a composition and process employing a medium that decreases toxicity. The present invention provides a such a composition and process.
It would be desirable to have a composition and process employing a medium that increases the efficiency of an exhaust after-treatment device of an internal combustion engine. The present invention provides such a composition and process.
It would be desirable to have a composition and process employing a medium that decreases emission of one or more regulated components from the exhaust of an internal combustion engine. The present invention provides such a composition and process.
It would be desirable to have a composition and process employing a medium that maintains or increases engine cleanliness. The present invention provides such a composition and process.